Add PM25 Kit example

Author: Tinyu-Zhao

examples/KIT/PM25/DFRobot_SHT20.cpp

@@ -0,0 +1,114 @@
+#include "DFRobot_SHT20.h"
+
+void DFRobot_SHT20::initSHT20(TwoWire &wirePort)
+{
+    i2cPort = &wirePort;
+    i2cPort->begin();
+}
+
+uint16_t DFRobot_SHT20::readValue(byte cmd)
+{
+    i2cPort->beginTransmission(SLAVE_ADDRESS);
+    i2cPort->write(cmd);
+    i2cPort->endTransmission();
+    byte toRead;
+    byte counter;
+    for(counter = 0, toRead = 0 ; counter < MAX_COUNTER && toRead != 3; counter++){
+        delay(DELAY_INTERVAL);
+        toRead = i2cPort->requestFrom(SLAVE_ADDRESS, 3);
+    }
+    if(counter == MAX_COUNTER){
+        return (ERROR_I2C_TIMEOUT);
+    }
+    byte msb, lsb, checksum;
+    msb = i2cPort->read();
+    lsb = i2cPort->read();
+    checksum = i2cPort->read();
+    uint16_t rawValue = ((uint16_t) msb << 8) | (uint16_t) lsb;
+    if(checkCRC(rawValue, checksum) != 0){
+        return (ERROR_BAD_CRC);
+    }
+    return rawValue & 0xFFFC;
+}
+
+float DFRobot_SHT20::readHumidity(void)
+{
+    uint16_t rawHumidity = readValue(TRIGGER_HUMD_MEASURE_NOHOLD);
+    if(rawHumidity == ERROR_I2C_TIMEOUT || rawHumidity == ERROR_BAD_CRC){
+        return(rawHumidity);
+    }
+    float tempRH = rawHumidity * (125.0 / 65536.0);
+    float rh = tempRH - 6.0;
+    return (rh);
+}
+
+float DFRobot_SHT20::readTemperature(void)
+{
+    uint16_t rawTemperature = readValue(TRIGGER_TEMP_MEASURE_NOHOLD);
+    if(rawTemperature == ERROR_I2C_TIMEOUT || rawTemperature == ERROR_BAD_CRC){
+        return(rawTemperature);
+    }
+    float tempTemperature = rawTemperature * (175.72 / 65536.0);
+    float realTemperature = tempTemperature - 46.85;
+    return (realTemperature);
+}
+
+void DFRobot_SHT20::setResolution(byte resolution)
+{
+    byte userRegister = readUserRegister();
+    userRegister &= B01111110;
+    resolution &= B10000001;
+    userRegister |= resolution;
+    writeUserRegister(userRegister);
+}
+
+byte DFRobot_SHT20::readUserRegister(void)
+{
+    byte userRegister;
+    i2cPort->beginTransmission(SLAVE_ADDRESS);
+    i2cPort->write(READ_USER_REG);
+    i2cPort->endTransmission();
+    i2cPort->requestFrom(SLAVE_ADDRESS, 1);
+    userRegister = i2cPort->read();
+    return (userRegister);
+}
+
+void DFRobot_SHT20::writeUserRegister(byte val)
+{
+    i2cPort->beginTransmission(SLAVE_ADDRESS);
+    i2cPort->write(WRITE_USER_REG);
+    i2cPort->write(val);
+    i2cPort->endTransmission();
+}
+
+byte DFRobot_SHT20::checkCRC(uint16_t message_from_sensor, uint8_t check_value_from_sensor)
+{
+    uint32_t remainder = (uint32_t)message_from_sensor << 8;
+    remainder |= check_value_from_sensor;
+    uint32_t divsor = (uint32_t)SHIFTED_DIVISOR;
+    for(int i = 0 ; i < 16 ; i++){
+        if(remainder & (uint32_t)1 << (23 - i)){
+            remainder ^= divsor;
+        }
+        divsor >>= 1;
+    }
+    return (byte)remainder;
+}
+
+void DFRobot_SHT20::showReslut(const char *prefix, int val)
+{
+    Serial.print(prefix);
+    if(val){
+        Serial.println("yes");
+    }else{
+        Serial.println("no");
+    }
+}
+
+void DFRobot_SHT20::checkSHT20(void)
+{
+    byte reg = readUserRegister();
+    showReslut("End of battery: ", reg & USER_REGISTER_END_OF_BATTERY);
+    showReslut("Heater enabled: ", reg & USER_REGISTER_HEATER_ENABLED);
+    showReslut("Disable OTP reload: ", reg & USER_REGISTER_DISABLE_OTP_RELOAD);
+}

examples/KIT/PM25/DFRobot_SHT20.h

@@ -0,0 +1,52 @@
+#ifndef DFRobot_SHT20_h
+#define DFRobot_SHT20_h
+
+#if defined(ARDUINO) && ARDUINO >= 100
+ #include "Arduino.h"
+#else
+ #include "WProgram.h"
+#endif
+#include <Wire.h>
+
+#define ERROR_I2C_TIMEOUT                     998
+#define ERROR_BAD_CRC                         999
+#define SLAVE_ADDRESS                         0x40 
+#define TRIGGER_TEMP_MEASURE_HOLD             0xE3
+#define TRIGGER_HUMD_MEASURE_HOLD             0xE5
+#define TRIGGER_TEMP_MEASURE_NOHOLD           0xF3
+#define TRIGGER_HUMD_MEASURE_NOHOLD           0xF5
+#define WRITE_USER_REG                        0xE6
+#define READ_USER_REG                         0xE7
+#define SOFT_RESET                            0xFE
+#define USER_REGISTER_RESOLUTION_MASK         0x81
+#define USER_REGISTER_RESOLUTION_RH12_TEMP14  0x00
+#define USER_REGISTER_RESOLUTION_RH8_TEMP12   0x01
+#define USER_REGISTER_RESOLUTION_RH10_TEMP13  0x80
+#define USER_REGISTER_RESOLUTION_RH11_TEMP11  0x81
+#define USER_REGISTER_END_OF_BATTERY          0x40
+#define USER_REGISTER_HEATER_ENABLED          0x04
+#define USER_REGISTER_DISABLE_OTP_RELOAD      0x02
+#define MAX_WAIT                              100
+#define DELAY_INTERVAL                        10
+#define SHIFTED_DIVISOR                       0x988000
+#define MAX_COUNTER                           (MAX_WAIT/DELAY_INTERVAL)
+
+class DFRobot_SHT20 
+{
+public:
+    void     checkSHT20(void);
+    void     setResolution(byte resBits);
+    void     writeUserRegister(byte val);
+    void     initSHT20(TwoWire &wirePort = Wire);
+    void     showReslut(const char *prefix, int val);
+    float    readHumidity(void);
+    float    readTemperature(void);
+    byte     readUserRegister(void);
+
+private:
+    TwoWire *i2cPort;
+    byte     checkCRC(uint16_t message_from_sensor, uint8_t check_value_from_sensor);
+    uint16_t readValue(byte cmd);
+};
+
+#endif